Insect bait stations are known in the art, wherein target insects are encouraged to retrieve a bait that may comprise or contain a component that is harmful to the target insect, for example, an insecticide that does not immediately disable the insect. The target insect transports some amount of the bait (including a delayed-action poison active ingredient) to the nest, which provides more effective eradication. For example, a pest control bait station is disclosed in U.S. Pat. No. 8,156,684, to Kirkland et al., and U.S. Patent Pre-Grant Application Publication No. 2014/0082994, to Mayo, Jr., both of which are hereby incorporated by reference. The bait station disclosed in Kirkland et al. comprises a multi-compartment tray defining separated bait reservoirs, with raised regions providing access, and a conveyance structure from the access apertures into the reservoir. However, the device is relatively complex, and therefore expensive, and it provides only one mode for the target insect to access the bait. Current bait stations on the market for ant control are typically food-based, and include gel baits, liquid baits, and solid granular baits.
As a major part of pest control operations, commercial toxic baits and/or bait stations have been used in both urban and agricultural settings. There are many types of bait stations in both commercial and consumer markets for various pest insects, such as ants, cockroaches, termites, etc. They typically consist of an attractant (e.g., food-based proteins, carbohydrates, or lipids), a carrier, and an active insecticide ingredient. Typically, the bait formulations in containerized devices (stations) are either a thick paste or solid blocks (with no or little water content) in reservoirs. Liquid baits, mainly the sugar-water based baits for several sugar-eating ant species are normally entrapped in closed or liquid-tight sealed containers during the storage and open to the target insects by consumers or pest control personnel by cutting off a small part of container or peeling away the seal. The major drawbacks of liquid baits are that they are typically less effective at attracting many protein/fat eating ant species, and they are susceptible to spillage.
Gel formulations are often preferable to thick paste or solid formulations due to the high water contents (40-80%) in the gel, which accommodates insect feeding preference and controls efficacy. In conventional systems, the gel is packed in syringes or squeeze tubes for direct applications in ant or cockroach infested sites such as cracks, crevices, and voids. Due to the high moister content in gels, current bait station designs are not able to contain or hold gel bait formulations for long periods of time, e.g., during the production, storage, shipping, and display of the product. Therefore, new and inexpensive bait station design concepts suitable for all bait formulations are needed to address above-mentioned issues.
Prior art ant baits have had only limited success. Such baits have not been as effective as they could be because the baits, and bait deployment, have failed to take into account the behavioral characteristics of the target ant, and the impact that biological needs of the ant (and ant colony) will have on these behavioral characteristics.
Ants (>14,000 spp. described; at least 20,000 spp. in nature worldwide) will eat almost anything, including sugars (honeydews, nectars), proteins (live or dead insects) and lipids (soybean or peanut oil). They also require water. Some species, like the leaf-cutter ants (Atta and Acromyrmex), use leaves to produce fungi in their nests as a food source. Harvester ants (e.g., Pogonomyrmex) collect seeds to store food. Some species even use aphids or scale insects, as if they were their cows, for their honeydew secretions. Some species forage by going to various fruits and flowers to collect nectar, for example honey pot ants, whereas other species prefer lipids-rich foods, such as soybean oil or peanut oil, for example imported fire ants.
In general, worker ants (e.g., foragers, nurses, guards) eat sugar-based foods (carbohydrates) in liquid form for energy; ant larvae eat proteins for growth in liquid, semi-liquid or solid forms; whereas queens need to have proteinaceous foods for reproductions and some sugar for energy in liquid or semi-liquid form. Ant larvae can consume solid foods, but adult ants (workers, males and queens) cannot. Worker ants can ingest some solid foods but cannot efficiently digest them. Even though foraging workers could transfer large size of solid protein foods (by mouthparts) or ingest small size of solid particles (by crop), they have a limited ability to digest bulky proteinaceous foods in the mid-gut because of a combination of their narrow waist (petiole) separating the thorax from the abdomen and producing only very small amounts of proteases in their mid-guts. Foraging workers can ingest small solid particles (<0.5 microns), due to the size of the buccal tube that is lined with setae and serve as filters in the ant head. Particles too large to pass through this filtering mechanism remain in the infrabuccal pocket, but can later be transferred by foragers to larvae in the colony.
The larvae, especially the later instars are capable of protein digestion of these large solid protein particles (even in an undigested state) both extra-orally through high protease levels in labial gland secretions and in the mid-gut. The later instars of larvae will feed back some of the digested/liquefied proteins to workers for sharing with young larvae or queens, or the minor nutrient needs for workers. Thus, larvae are not only the passive recipients of nutrition (proteins), but also an active protein digestive organ for the colony. The younger larvae, on the other hand, eat mainly the liquefied, or at least semi-liquefied, proteins provided by workers (directly obtained from field by foragers or fed back from older larvae via workers).
Forager workers handle liquid foods much quicker and more efficiently than solid foods. Liquids, especially sugar-based liquids, are easily ingested through the worker buccal tube into the pharynx and down the esophagus to the crop and mid-gut for storage and digestion. The liquid sugar foods will be transferred to the nest for sharing with other workers, queens and of course for their own energy needs.
Protein provides amino acids that are used predominately by larvae to grow, while carbohydrates are used mostly by workers as a substrate for energy. Larvae play an important role in protein regulation behavior; ant colonies that lack brood prefer carbohydrate-biased diets, while those with brood prefer a more balanced protein-carbohydrate intake. However, too much protein can be toxic for ants. Therefore, regulating protein intake to a fixed level is a mechanism for keeping the entire colony healthy.
Carbohydrates, in contrast to protein, are equally valuable for both workers and larvae. In workers, carbohydrates fuel foraging activities and can be used to build lipid reserves, and in larvae they can enhance development when matched with dietary protein.
The insect fat body is a tissue composed of lobes suspended in the hemocoel, or primary body cavity, and bathed in the insect hemolymph. The fat body plays major roles in the life of insects. It is a dynamic tissue involved in multiple metabolic functions, including the storing and release of energy in response to the energy demands of the insect. Lipid is the main fat body component, and more than 90% of the lipid stored is triglyceride (TAG), which can be synthesized from dietary carbohydrates, fatty acids, or proteins. The key function of fat body is to store and release energy in response to the energy demands of ants. Only a few ant species, such as fire ants, are attracted to and actively forage the lipid-rich food (or baits; such as granules of defatted corn grit impregnated with soybean oil). Most ant species do not actively forage lipids, but they are able to convert sugars (carbohydrates) and/or proteins to lipid.
The decision of a forager to retrieve an encountered food item is influenced by both internal and external factors, occurring at both the individual and colony level. At the individual level, a worker's current physiological condition (e.g., endogenous stores of lipids) may prompt foraging behavior. The attractiveness of an encountered food item may be affected by the perceived relative availability and/or abundance or scarcity of food items. At the colony level, feedback related to larval nutritional demands (especially for protein), transmitted through a ‘chain-of-demand’ between brood, nurse workers, and foragers, and created through colony member food sharing is likely to be important. However, the strength of both internal and external cues directing worker foraging decisions can vary temporally, compounding the task of nutrient retrieval especially in the face of potential resource shortfalls (e.g., seasonal variation in resource availability). Potential determinants guiding the collection of resources by workers might include, but are not limited to, resource preference of different colony members, temporal shifts in resource availability and worker preference and food distribution among colony members.
Baits work by taking advantage of ant biology and behavior such as social grooming and trophallaxis (food sharing). Once a bait is discovered, foraging ants collect the bait and transport it back to the colony. They will communicate the location and quality of the food sources (baits) to other foragers in the colony via trail pheromone; the other workers will follow pheromone trail(s) to the newly discovered bait. Those workers retrieve the bait and return to the colony, also re-enforcing the pheromone trail laid down by the first group of foragers. In a short period of time many workers will follow the foraging trail, quickly arriving at the bait source, and transfer the bait back to the nest for sharing with other members of the colony.
The brood, especially late instars, may be important in the digestion of solid bait particles into a liquefied form that can be transferred to workers and reproductives in the colony. The amount of brood in the colonies could be responsible for the foraging preference and behavior of the worker ants. Fourth instar larvae do most of the protein digestion in the ant colony and their presence in a colony can change ant foraging preference to proteinaceous materials.
It is through food sharing that toxicant in the bait can be transferred to the rest of the colony. Because the bait is picked up directly by the ant forager workers and is later shared within the colony, relatively low amounts of the toxicant can be used in targeting a pest ant population. Ant foragers that first pick up or consume the bait, share the toxicant within the bait with other workers, queen tenders, and larvae. Typically after 3-4 days the toxicant will reach the queen, which affects reproduction in the colony. Even if the queen dies, eggs may hatch, larvae may pupate and develop into workers. The final control of a large ant colony may take 1-5 months.
A bait station with multiple compartments/chambers with different food bait types (e.g., sugar, protein, or lipid) could meet all the variable nutritional demands of the colony at both the individual and the colony levels throughout the season (regardless of ant species). The presence of all potential nutrients in separated forms in our bait station should increase the likelihood that foraging ants find what they need, and communicate the location and quality of the food sources (baits) to other foragers via pheromones. Such a bait station design would not only significantly increase ant foraging activities and the overall nutrient acquisition efficacy, but more importantly will increase and maximize the transfer and distribution of a lethal dose of insecticide with delayed toxicity to all members of the colony, especially to larvae and queen(s) through the protein bait intake, before foraging and food sharing activities are shut down (due to the toxic active ingredient in the baits) in the colony; and ultimately kill all castes within the nest (workers, larvae, males, and queens) for elimination of the ant colony.